1. Field of the Invention
The present invention relates to an image forming apparatus capable of transferring a toner image onto a recording material on a recording material conveying member that bears and bears the recording material.
2. Description of the Related Art
Recently, image forming apparatuses using an electrophotographic process are experiencing advancements toward higher speed, higher functions and color capability, and printers and copying machines of various types are commercially available. For example, an image forming apparatus of in-line type, in which image forming units a plurality of colors are arranged serially to execute multiple transfers of toner images in succession, is adopted as a color printer.
Within such image forming apparatus of an in-line type, there is known an image forming apparatus of this type that forms a full-color image by transferring toner images in succession from serially-arranged image forming units onto a belt-shaped intermediate transfer member. Then, the images on the intermediate transfer member are collectively transferred onto a recording material (sheet), for example borne on a belt-shaped conveying unit to form a recorded image. In another process, toner images are transferred in succession, from serially-arranged image forming units, directly onto a recording material borne on the surface of a conveyor belt in superposed manner to form a full-color image.
On the other hand, also known is an image forming apparatus in which, at the transfer of a toner image on a photosensitive member serving as an image bearing member or on an intermediate transfer member onto a recording material, the recording material is borne on a conveyor belt and conveyed to a transfer position. This process has an advantage that the behavior of the recording material is stabilized at the transfer position. In the case of bearing the recording material on the conveyor belt, an adhering member is utilized. The recording material is introduced between the conveyor belt and the adhering member, and a voltage is applied to the adhering member while the recording material passes a position opposed to the adhering member. Thus, the recording material is charged and electrically adhered to the conveyor belt, whereby the recording material can be fixed to the conveyor belt.
However, the recording material adhered to the conveyor belt as described above tends to cause, when separated from the conveyor belt, a separating discharge between the surface of the conveyor belt and the rear surface of the recording material. Therefore, in the case that a toner image is transferred onto the recording material borne on the conveyor belt, the toner image on the recording material is blurred by the influence of the separating discharge. In particular, blurring of the toner image by the separating discharge becomes conspicuous in a trailing edge portion in the moving direction of the recording material. This is because, in the course of separation of the recording material from the conveyor belt, the charge on the recording material may not lead to a discharge by being displaced on the recording material but loses a place of escapement, when the recording material is completely separated from the conveyor belt, thereby tending to cause a discharge. Also image blurring tends to be caused more conspicuously at the trailing edge of the recording material, because of instability in the separating direction.
Such image blurring is generated when a recording material, bearing an unfixed toner, is separated from the conveying member, and is generated not only in the image forming apparatus of intermediate transfer process utilizing an intermediate transfer belt and a conveyor belt, but also in the image forming apparatus of a direct transfer process described above.